Imaging optical system, illuminating device, and microscope apparatus

Abstract

Provided is an imaging optical system including: a plurality of imaging lenses that form a final image and at least one intermediate image; a first phase modulation element that is disposed closer to an object than any of the at least one intermediate image is and that gives a spatial disturbance to the wavefront of light from the object; and a second phase modulation element that is disposed at a position so as to sandwich the at least one intermediate image with the first phase modulation element and that cancels out the spatial disturbance given to the wavefront of the light from the object by the first phase modulation element. The imaging lenses are configured so as to satisfy Herschel's condition.

1 . An imaging optical system comprising:
 a plurality of imaging lenses that form a final image and at least one intermediate image;   a first phase modulation element that is disposed closer to an object than any of the at least one intermediate image formed by the imaging lenses is and that gives a spatial disturbance to a wavefront of light from the object; and   a second phase modulation element that is disposed at a position so as to sandwich the at least one intermediate image with the first phase modulation element and that cancels out the spatial disturbance given to the wavefront of the light from the object by the first phase modulation element,   wherein the imaging lenses are configured so as to satisfy Herschel's condition.   
     
     
         2 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element are disposed at optically conjugate positions. 
     
     
         3 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element are disposed in the vicinities of pupil positions of the imaging lenses. 
     
     
         4 . An imaging optical system according to  claim 1 , further comprising an optical-path-length varying portion that can change an optical path length between the two imaging lenses, which are disposed at positions so as to sandwich any of the at least one intermediate image therebetween. 
     
     
         5 . An imaging optical system according to  claim 4 , wherein the optical-path-length varying portion is provided with: a plane mirror that is disposed perpendicular to an optical axis and that reflects, so as to turn around, light formed into the intermediate image; an actuator that moves the plane mirror in the optical axis direction; and a beam splitter that splits off the light reflected at the plane mirror in two directions. 
     
     
         6 . An imaging optical system according to  claim 1 , further comprising a variable spatial phase modulation element that is disposed in the vicinity of a pupil position of one of the imaging lenses and that changes spatial phase modulation to be applied to the wavefront of light, thereby changing a position of the final image in the optical axis direction. 
     
     
         7 . An imaging optical system according to  claim 6 , wherein function of at least one of the first phase modulation element and the second phase modulation element is performed by the variable spatial phase modulation element. 
     
     
         8 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element apply, to the wavefront of a light flux, phase modulations that change in a one-dimensional direction perpendicular to the optical axis. 
     
     
         9 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element apply, to the wavefront of a light flux, phase modulations that change in two-dimensional directions perpendicular to the optical axis. 
     
     
         10 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element are transmissive elements that apply phase modulations to the wavefront of light when the light is transmitted therethrough. 
     
     
         11 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element are reflective elements that apply phase modulations to the wavefront of light when the light is reflected thereat. 
     
     
         12 . An imaging optical system according to  claim 1 , wherein the first phase modulation element and the second phase modulation element have complementary shapes. 
     
     
         13 . An imaging optical system according to  claim 10 , wherein the first phase modulation element and the second phase modulation element apply, to the wavefront, phase modulations through refractive-index distributions of transparent materials. 
     
     
         14 . An illuminating device comprising:
 an imaging optical system according to  claim 1 ; and   a light source that is disposed on the object side of the imaging optical system and that produces illumination light to be made to enter the imaging optical system.   
     
     
         15 . A microscope apparatus comprising:
 an imaging optical system according to  claim 1 ; and   a photodetector that is disposed on the final image side of the imaging optical system and that detects light produced in an observation object.   
     
     
         16 . A microscope apparatus according to  claim 15 , wherein the photodetector is an image acquisition device that is disposed at a position of the final image of the imaging optical system and that acquires the final image. 
     
     
         17 . A microscope apparatus comprising:
 an imaging optical system according to  claim 1 ;   a light source that is disposed on the object side of the imaging optical system and that produces illumination light to be made to enter the imaging optical system; and   a photodetector that is disposed on the final image side of the imaging optical system and that detects light produced in an observation object.   
     
     
         18 . A microscope apparatus according to  claim 17 , further comprising a Nipokow-disk confocal optical system that is disposed among the light source, the photodetector, and the imaging optical system. 
     
     
         19 . A microscope apparatus according to  claim 17 ,
 wherein the light source is a laser light source; and   the photodetector is provided with a confocal pinhole and a photoelectric conversion element.   
     
     
         20 . A microscope apparatus comprising:
 an illuminating device according to  claim 14 ; and   a photodetector that detects light produced in an observation object irradiated by the illuminating device,   wherein the light source is a pulse laser light source.   
     
     
         21 . A microscope apparatus according to  claim 19 , further comprising an optical scanner,
 wherein the optical scanner is disposed at a position optically conjugate with the first phase modulation element, the second phase modulation element, and pupils of the imaging lenses.   
     
     
         22 . A microscope apparatus according to  claim 20 , further comprising an optical scanner,
 wherein the optical scanner is disposed at a position optically conjugate with the first phase modulation element, the second phase modulation element, and pupils of the imaging lenses.